Electron discharge device of the electron velocity modulation type



Sept. 26, 1950 s. G. TOMLlN 2,523,344

ELECTRON DISCHARGE DEVICE OF THE ELECTRON VELOCITY MODULATION TYPE Filed Oct. 6, 1945 F/G./. H02

. 28 8 28 I/B v2 V w A 2O A 22 lMIMMMll/m Patented Sept. 26, 1950 ELECTRON DISCHARGE DEVICE OF THE ELECTRON VELOCITY MODULATION TYPE Stanley Gordon Tomlin, London, England, as-

signor, by mesne assignments, to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application October 6, 1945, Serial No. 620,815 In Great Britain September 1, 1944 Section 1, Public Law 690, August 8, 1946 Fatent expires September 1, 1964 The present invention relates to electron discharge devices of the electron velocity modulation type, and concerns particularly a device having a new form of resonator derived from a transmission line consisting of a screened pair of conductors.

Theoretical considerations indicate that the efiiciency of a high frequency generator of the velocity modulation type can be increased by providing more than two gaps for the interchange of energy between the electron beam and the resonator or resonators. Various devices are already known in which a beam of electrons is fired through three or more separate resonating systems which may be coupled in some suitable way, or past three or more gaps communicating with a single resonator. The present invention covers a device of the latter type in which the single resonator comprises a section of a screened pair transmission line, the electrons being fired transversely across the resonator so as to pass through both the conductors of the pair. The arrangement is like the coaxial line type of resonator described in United States Patent No. 2,320,860 issued to John Heaver Fremlin on June 1, 1943, but there are two inner conductors instead of only one, and three gaps instead of two. The same ideas may be extended to apply to a resonator having more than two conductors arranged inside a screen, the electrons being fired transversely across the resonator soas to pass through all the inner conductors. The invention accordingly provides an electron discharge device of the electron velocity modulation type comprising a hollow resonator consisting of a plurality of conductors arranged inside an elongated conducting screen, and separated from each other and from the screen by a series of gaps, and means for projecting a beam of electrons across the said resonator transversely to the axis thereof so as to pass through an aperture in each of the said conductors and past each of the said gaps.

The invention will be described with reference to the accompanying drawing in which- Figs. 1 and 2 show side views of a device according to the invention.

Fig. 3 shows a slightly enlarged transverse sectional view at AA of Fig. 1, and

Fig. 4 shows an enlarged longitudinal section of the resonator of Figs. 1 and 2 to show the internal details thereof.

The device comprises a tubular glass bulb I having an annular copper disc 2 sealed through its walls in known manner, the disc carrying a hollow cylindrical resonator 3 rigidly fixed thereto.

, 7 Claims. (01. 315-6) The details of the resonator 3 are shown more clearly in the axial section of Fig. 4. It consists of a thin walled metal tube 4 closed at the lower end by a shallow cup-like disc 5 to which. are attached two metal rods 6 and 1 equally spaced on either side of the axis of the tube. Those rods are united beyond the open end of the tube by a loop 8. A longitudinal slot is cut in each of the rods 6, 1 and in the corresponding opposite walls of the tube 4 so that a narrow transverse passage is thereby produced enabling a blade-like beam of electrons to be fired through it along the dotted line 9-H]. Pairs of fiat fins ll, l2, l3, [4 are provided on the walls of the resonator 3 and on the rods 6 and l forming walls for the transverse passage. This passage and the fins can be seen in the sectional view, Fig. 3. It will be seen that three gaps l5, 16, H are thereby formed, past which the electrons travel and excite the resonator.

The electron beam is generated by a cathode l 8, control electrode l9 and accelerator electrode 20, which may be arranged in the manner described in the above mentioned patent. The electrons after passing through the resonator are collected on a plate 2|. These various electrodes are mounted between mica sheets 22, 23, 24, the whole being supported on wires fromthe glass press 25 at the lower end of the bulb. A base 26 carries terminals 21 for the electrodes of the device.

The widths of the fins ll, l2, l3, l4 determine the widths of the gaps and the lengths of the electron drift spaces between the gaps, and will have the effect of capacity loading the resonator. Elementary considerations suggest that the length of the drift spaces should be such that the electrons spendabout 5 quarter periods and about 5 quarter periods, respectively, in the first and second drift spaces, though in practice these may not prove to be quite the best figures.

The electron velocity should be adjusted so that the two rods 6 and l oscillate in opposite phase, so that an oscillating current will then flow in the loop 8. In this case an H1 type wave may be generated in a wave guide or resonator coupled to the resonator 3. Such coupling may be effected, for example, by inserting the portion 28 of the bulb into the end of the guide so that the disc 2 forms the closing wall for the said end, according to well known practice. The

device may be tuned by tuning the external resonator to which it is coupled, for example by adjusting a piston, and power may be extracted from the guide or resonator by means of a loop or probe coupling according to known practice.

3 The loop 8 may, if desired, be replaced by an antenna system suitably connected to the rods 6 and 1.

It should be noted that the device oscillates as a half-wave or full wave resonator, the loop 8 being equivalent to a closed end. The device can there is no doubt which mode is being produced.

and no danger of jumping from one mode to the other.

What is claimed is:

1. An electron discharge device comprising a hollow resonator including a metal tubular portion and a metal disc disposed at one end of said tubular portion, a pair of conductors carried by said disc inside said tubular portion, said conductors being separated from each other and from the tubular portion thus providing a plurality of gaps each communicating with the common space around said conductors inside said tubular portion, the ends of said conductors being connected in the form of a loop for the flow of current therethrough, said tubular portion and said conductors being provided with a set of aper tures along said diameter passing through said resonator and each of said conductors, and means positioned adjacent said apertures for projecting a beam of electronsacross said resonator whereby the electrons in said beam excite oscillations in the resonator at each of said gaps.

2. An electron discharge device comprising a hollow resonator including a metal tubular por tion and a; metal disc closing one end thereof, a pair of rod conductors positioned on a diameter on said disc inside said tubular portion, said conductors being separated from each other and from said tubular portion thus providing a series of three gaps along said diameter, said gaps each communicating with the common space around said conductors inside said tubular portion, said tubular portion and conductors being provided 4 with a set of apertures along said diameter through said tubular portion, and means aligned With said apertures for projecting a beam of electrons across said resonator, whereby the electrons in said beam excite oscillations in said resonator at each of said aps.

3. An electron discharge device according to claim 2 comprising means connected to the free ends of said conductors for extracting the energy of the oscillations.

4. An electron discharge device according to claim 3 in which the said means comprises a metallic loop connecting the ends of the said conductors and extending beyond the open end of the said tubular portion.

5. An electron discharge device according to claim 4 in which the resonator and projecting means are enclosed in a glass envelope, the resonator being attached at the end opposite said closed end to a metal apertured disc sealed through the walls of the said envelope.

6. 'An electron discharge device according to claim 5 comprising an external hollow resonator coupled to the metal apertured disc about the said metallic loop, the said disc effectively forming part of a wall of the said external resonator, and means for tuning the external resonator.

'7. An electron discharge device according to claim 6 in which metal fins are attached to the said conductors and to the internal walls of the tubular portion in the neighbourhood of the said apertures for the purpose of defining the said gaps.

STANLEY GORDON TOMLIN.

REFERENCES CITED The following references are of record in the file of this patent: I

UNITED STATES PATENTS Number Name Date 2,128,232 Dallenbach Aug. 30, 1938 2,289,846 Litton July 14, 1942 2,320,860 Fremlin June 1, 1943 2,383,343 Ryan Aug. 21, 1945 2,416,299 Fr'emlin Feb. 25, 1947 2,434,962 Rostas Jan. 27, 1948 

